New York's underground park of the future
For New Yorkers frustrated by the lack of space the tradition has long been to build upwards - but the city renowned for its skyscrapers is now looking to exploit spaces underground too.
The Low Line is a proposed subterranean park the size of a football pitch that would be created on the site of a former trolley terminal in Manhattan's Lower East Side.
The century-old site has not been in use since 1948, yet its 18ft-high (5.5m) ceilings, rail tracks and cobblestones have been preserved largely intact.
The name Low Line echoes the hugely popular High Line. That public park was created on disused sections of a raised railway track that snakes through downtown Manhattan. It attracts millions of visitors each year.
The team behind the idea, Dan Barasch and James Ramsey, would love to give residents an alternative place to escape the city's crowded streets. But how to get trees and grass to grow so far underground?
A system of solar panels and fibre optics would be used to bring light from above ground down to the terminal. They insist the technology has the potential to support photosynthesis.
The park plan is in its early stages. A Kickstarter campaign this month raised the first $150,000. Mr Barasch admits the final cost is likely to be "many millions of dollars" and take several years.
Produced by Anna Bressanin; camera by Ilya Shnitser